Cancer is the second most common cause of death in the United States, exceeded only by heart disease. In the United States, cancer accounts for 1 of every 4 deaths. The 5-year relative survival rate for all cancers patients diagnosed in 1996-2003 is 66%, up from 50% in 1975-1977 (Cancer Facts & Figures American Cancer Society: Atlanta, Ga. (2008)). This improvement in survival reflects progress in diagnosing at an earlier stage and improvements in treatment. Discovering highly effective anticancer agents with low toxicity is a primary goal of cancer research.
2-aryl-thiazolidine-4-carboxylic acid amides have been described as potent cytotoxic agents for both prostate cancer and melanoma (Li et al., “Synthesis and Antiproliferative Activity of Thiazolidine Analogs for Melanoma,” Bioorg. Med. Chem. Lett. 17:4113-7 (2007); Li et al., “Structure-Activity Relationship Studies of Arylthiazolidine Amides as Selective Cytotoxic Agents for Melanoma,” Anticancer Res. 27:883-888 (2007); Lu et al., “Synthesis and Biological Evaluation of 2-Arylthiazolidine-4-Carboxylic Acid Amides for Melanoma and Prostate Cancer,” Abstracts of Papers, 234th ACS National Meeting, Boston, Mass., United States, Aug. 19-23, 2007, MEDI-304; Gududuru et al., “SAR Studies of 2-Arylthiazolidine-4-Carboxylic Acid Amides: A Novel Class of Cytotoxic Agents for Prostate Cancer,” Bioorg. Med. Chem. Lett. 15:4010-4013 (2005); Gududuru et al., “Discovery of 2-Arylthiazolidine-4-Carboxylic Acid Amides as a New Class of Cytotoxic Agents for Prostate Cancer,” J. Med. Chem. 48:2584-2588 (2005)). These 2-aryl-thiazolidine-4-carboxylic acid amides were designed from lysophosphatidic acid (LPA) structure with a lipid chain. This design choice was directed toward inhibition of GPCR (guanine-binding protein-coupled receptor) signaling, which is involved in proliferation and survival of prostate cancer (Raj et al., “Guanosine Phosphate Binding Protein Coupled Receptors in Prostate Cancer: A Review,” J. Urol. 167:1458-1463 (2002); Kue et al., “Essential Role for G Proteins in Prostate Cancer Cell Growth and Signaling,” J. Urol. 164:2162-7 (2000); Guo et al., “Expression and Function of Lysophosphatidic Acid LPA1 Receptor in Prostate Cancer Cells,” Endocrinology 147:4883-4892 (2006); Qi et al., “Lysophosphatidic Acid Stimulates Phospholipase D Activity and Cell Proliferation in PC-3 Human Prostate Cancer Cells,” J. Cell. Physiol. 174:261-272 (1998)).
The most potent of the 2-aryl-thiazolidine-4-carboxylic acid amides could inhibit prostate cancer cells with an average IC50 in the range from 0.7 to 1.0 μM and average IC50 values against melanoma cells were 1.8˜2.6 μM (Li et al., “Synthesis and Antiproliferative Activity of Thiazolidine Analogs for Melanoma,” Bioorg. Med. Chem. Lett, 17:4113-7 (2007)). One preferred compound, (2RS,4R)-2-phenyl-thiazolidine-4-carboxylic acid hexadecylamide, was sent to the United States National Cancer Institute 60 human tumor cell line anticancer drug screen (NCI-60). Results from NCI-60 assay showed that this compound could inhibit growth of all nine types of cancer cells with IC50 values in the range from 0.124 μM (Leukemia, CCRF-CEM) to 3.81 μM (Non-Small Cell Lung Cancer, NCI-H522). Further improvement in anti-cancer activity of these compounds, in terms of their IC50 values, would be desirable.
The present invention is directed to overcoming these and other deficiencies in the prior art.